Salmon Aquaculture and Antimicrobial Resistance in the Marine Environment

Alejandro H Buschmann,Fred Moy,Miguel A Maldonado,Felipe C Cabello,Alexandra Tomova,Larisa Ivanova,Luis A Henríquez,Alejandra López,Henry P Godfrey,Martin Krkosek

doi:10.1371/journal.pone.0042724

Alejandro H Buschmann, Fred Moy + Show 8 more

Open Access

https://doi.org/10.1371/journal.pone.0042724

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Journal: PloS one	Publication Date: Aug 8, 2012
Citations: 225	License type: CC BY 4.0

Affiliation: University of Los Lagos, New York Medical College

Abstract

Antimicrobials used in salmon aquaculture pass into the marine environment. This could have negative impacts on marine environmental biodiversity, and on terrestrial animal and human health as a result of selection for bacteria containing antimicrobial resistance genes. We therefore measured the numbers of culturable bacteria and antimicrobial-resistant bacteria in marine sediments in the Calbuco Archipelago, Chile, over 12-month period at a salmon aquaculture site approximately 20 m from a salmon farm and at a control site 8 km distant without observable aquaculture activities. Three antimicrobials extensively used in Chilean salmon aquaculture (oxytetracycline, oxolinic acid, and florfenicol) were studied. Although none of these antimicrobials was detected in sediments from either site, traces of flumequine, a fluoroquinolone antimicrobial also widely used in Chile, were present in sediments from both sites during this period. There were significant increases in bacterial numbers and antimicrobial-resistant fractions to oxytetracycline, oxolinic acid, and florfenicol in sediments from the aquaculture site compared to those from the control site. Interestingly, there were similar numbers of presumably plasmid-mediated resistance genes for oxytetracycline, oxolinic acid and florfenicol in unselected marine bacteria isolated from both aquaculture and control sites. These preliminary findings in one location may suggest that the current use of large amounts of antimicrobials in Chilean aquaculture has the potential to select for antimicrobial-resistant bacteria in marine sediments.

Highlights

It is believed that aquaculture will constitute the source of over more than half of the seafood consumed in the world in coming years because of the collapse of natural fisheries [1]
Flumequine was present in four sediment samples from the control site, 8 km from the aquaculture site (Fig. 1): one in December, 2008, two in January, 2009 and one in April, 2009
We studied marine sediments from two sites in the Calbuco Archipelago in southern Chile to determine numbers of culturable and antimicrobial-resistant bacteria they contained

Summary

Introduction

It is believed that aquaculture will constitute the source of over more than half of the seafood consumed in the world in coming years because of the collapse of natural fisheries [1]. This optimistic view needs to be tempered by increasing information suggesting such expansion may be unsustainable as aquaculture generates untoward effects such as habitat destruction, eutrophication and environmental contamination with chemicals and antimicrobials [2]. In Chile, this growth has been accompanied by major mortalities of salmon reared in net pens These can reach 50% of production under some conditions with ensuing large economic losses [16,17]. Conservative estimates suggest that approximately 950 metric tons of quinolones were used in salmon aquaculture in Chile between 2000 and 2008, and approximately 1500 metric tons of tetracycline and 478 metric tons of florfenicol were used for this purpose between 2000 and 2007 [23,24,25]

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